SW6110103_Response To Comments_20230503

AECOM
JSOC, SOF C4 Facility (LI66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
03 May 2023
USACE Project No. PN97470
AECOM Project No. 60652522
Additional information was requested by NCDEQ State Stormwater Engineer Jim Farkas, in a letter dated April
28, 2023. The original comments are enumerated below with AECOM responses below each comment.
1. Prior Comment 1— "Please ensure that the proposed SCM is sized/designed based on the actual
drainage area to the SCM. Per 15A NCAC 02H.1003(3)(b), any off -site or existing BUA that is not
bypassed around the SCM must be accounted for in the sizing of the SCM." The Supplement-EZ Form
and other submittal items indicate that the drainage area of the bioretention cell is 23,647 sf with a total
of 17,466 sf of BUA. Using the Simple Method to determine the minimum required volume for the SCM
results in a minimum required treatment volume of 1,409 cf (Rv = 0.05 + 0.9*(17,466 sf123,647 sf) =
0.715, Rd = 1.0'; & DA = 23,647 sf -> V = Rv * Rd * DA = 0.715 * 1.0" * 23,467 sf = 1,409 cf) whereas
the calculations indicate 1,074 cf (which appears to exclude the existing BUA from the drainage area to
the SCM. NOTE: While you are not required to treat existing BUA, any existing BUA that is not
bypassed around the SCM must be accounted for in the sizing of the SM (per 15A NCAC 02H
.1003(3)(b)). The provided stage -storage tables indicate that less than 1,409 cf of storage will be
provided between the planting surface of the bioretention cell (elevation 264.0) and the invert of the
lowest bypass (elevation 264.75'). Please revise as needed. NOTE: The provided stage -storage table
includes storage volume provided below the planting surface elevation (The cumulative storage volume
at elevation 264.0' is shown as 210 cf, but should be zero since storage provided below the planting
surface does not count towards the design volume of the SCM). Please revise as needed..
AECOM Response: The Supplement-EZ Form and Hydrology Report with supporting calculations
have been revised to account for both new and existing BUA within the bioretention SCM
drainage area. The outlet structure has been revised for maximum ponding elevation of 265.0',
corresponding to a maximum ponding depth of 12-inches. This provide a stage -storage volume
of 1,419 cf, which is greater than the required 1,409 cf. The stage -storage table has also been
revised to remove storage below the planting elevation of 264.0'.
2. For the sake of clarity/ would like to verify that the following information is correct (Please let me know if
it is not):
a. The entire proposed project area is 147,233 sf. Correct.
b. The total amount of BUA that will exist within the entire proposed project area (whether new,
existing, or otherwise) will be 94,139 sf once construction is complete. Correct.
c. The net increase in the amount of BUA within the entire proposed project area from what was
previously permitted/existing to the amount of BUA that will exist within the entire project area
once construction is complete is 9,041 sf. Correct.
d. The total drainage area to the infiltration trench (that was previously permitted) will be 85,000 sf
once construction is complete. Correct.
e. The total amount of BUA that will exist within the drainage area to the infiltration trench (whether
new, existing, off -site, or otherwise) will be 58,947 sf once construction is complete. Correct.
f. The total drainage area to the bioretention cell will be 23,647 sf once construction is complete.
Correct.
g. The total amount of BUA that will exist within the drainage area to the bioretention cell (whether
new, existing, or otherwise) will be 17,466 sf once construction is complete. Correct.
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AECOM
JSOC, SOF C4 Facility (1-I66362) and Microgrid Installation & Integration
Responses to NCDEQ Request for Additional Information
03 May 2023
USACE Project No. PN97470
AECOM Project No. 60652522
AECOM Response: See above for confirmation.
3. Provide PDFs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other documents, and
a response to comments letter briefly describing how the comments have been addressed.
a. PDFs must be uploaded using the form at: hitps://edocs.deg,nc.gov/Forms/SW-Supplemental-
Upload
b. b. Hard copies must be mailed or delivered to the following address:
i. For FedEx/UPS:
Jim Farkas
512 N. Salisbury Street, Office 640M
Raleigh, NC 27604
ii. For LISPS:
Jim Farkas
1612 Mail Service Center
Raleigh, NC 27699-1612
iii. Hand Delivery:
Please reach out to me prior to hand delivering a submission to make sure that 1 (or someone
else in my group) will be able to receive the submission. Do not leave the package in the
foyer with the security guard. NOTE: Hard copies should not be sent to a Regional Office.
Doing so will delay the review process and the submission package may be lost while being
sent from the Regional Office to me in the Central Office.
AECOM Response: Noted. Revised PDFs will be uploaded with hard copies following.
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